I am interested in setting up a haunted attraction outside. The issue is I want to run it during the day. Has anybody tried this? My main concerns are the heat and a black tent not being enough to keep the sun out of the haunt.

You can use custom white black out poly banner material and have a custom tent made. This material is white on one side a black on the other and is designed for banners over window so the sun does not bleed through.

yeah definitely going to need some kind of blackout material. I have researched it a little bit, but if somebody has experience with some good material/fabric/tents it would be great if you could let me know! Thanks for the help.

I used to work for a major theme park and 2 of the 4 haunts we had were done in tents. They were made of the sun blocking material austind mentioned. There was sometimes light at the seams, but it was very minor- not enough to affect the show. It's the route I'd go if you're wanting it to be open and scary during those extended day hours. We had also had a haunted trail at the park and it opened during daylight too. Weak. Overall it was always the weakest of the 4 haunts we had but the daylight thing made it ultra cheesy.
There are also some modular "pop up" buildings out there- sort of between a tent and a hard structure. Dome shaped and light proof. Universal utilized one of these for their Penn & Teller New'kd Las Vegas haunt last year.